1. Field of the Invention
The present invention is directed to a mobile communication device and more particularly, to a mobile communication device using an antenna and a system ground plane to form a sensing capacitor.
2. Description of Related Art
During the development of the wireless communication, the Federal Communications Commission (hereinafter as FCC) has set up a specific absorption ratio (hereinafter as SAR) standard to restrict energy or the highest limitation that a mobile communication device is allowed to radiate so as to prevent an electromagnetic wave radiated from an antenna to harm human health.
In order to comply with the SAR value regulated by the FCC, in most of the currently existing mobile communication devices, a proximity sensor is commonly disposed around the antenna. The proximity sensor includes a sensing capacitor and a sensing controller. Thus, when a human body approaches the antenna, an electric charge of the sensing capacitor is changed in response to the approach of the human body. Moreover, the sensing controller instructs a system to lower down the antenna radiated power so as to prevent the overly high power absorbed by the human body.
However, in order to improve sensitivity of the sensing capacitor, a metal sheet used to form the sensing capacitor is usually designed in a large size. Besides, in actual configuration, the metal sheet of the sensing capacitor cannot be too close to the system ground plane so as to avoid a sensing capacitor failure. Further, the metal sheet of the sensing capacitor cannot be too close to the antenna, either so as to avoid influence on the antenna reception quality. Therefore, the metal sheet in the sensing capacitor often consumes enormous hardware space for being disposed in the mobile communication device, such that the miniaturization development of the mobile communication device is limited, and costs spent on material purchasing and working hours of assembly are increased due to additional disposition of the metal sheet when manufacturing.